PRODUCTION OF SILICON NITRIDE SINTERED BODY

摘要

PURPOSE:To omit troublesome stages as well as to shorten the time required to sinter a porous molded body of silicon nitride and to prevent the decomposition of the silicon nitride by treating the molded body having a film of metal powder or ceramic powder formed on the surface with a supercritical fluid, converting the film into a gas impermeable film by heating, and sintering the molded body. CONSTITUTION:Metal powder or ceramic powder is slurried and applied to a porous molded body of silicon nitride to form a film of the powder on the surface. The molded body having the film is immersed in a supercritical fluid to extract and remove extractable components in the molded body and a dispersion medium used and then the molded body is pretreated to convert the film into a gas impermeable film by heating. The pretreated molded body is sintered. The pretreatment is preferably carried out under ordinary pressure or under elevated pressure in an N2 atmosphere.